It has previously been proposed to form articles of sanitary ware, such as lavatories and bathtubs, as polyester-melamine formaldehyde laminates. In such cases the polyester functions as a reinforcing substrate, and the melamine-formaldehyde resin or glaze functions as a hard glossy glaze on the polyester surface. The polyester contributes certain useful properties to the laminate, such as low weight, rigidity and toughness, good impact strength, and low material cost. The melamine-formaldehyde glaze contributes certain useful properties such as good stain resistance (iodine, hair spray, household cleansers, etc.), good gloss retention, satisfactory abrasion resistance, good heat resistance (cigarette burns, etc.), and good scratch resistance. The melamine-formaldehyde resin is relatively expensive. Therefore its use as a thin glaze is helpful in reducing the cost of the laminate.
Unfortunately it has been found difficult to bond the melamine resin directly on conventional cross linked polyesters which use styrene as a cross linking agent. The glaze tended to peel, blister or lose gloss when subjected to boiling water and other tests simulating service conditions.
An object of the present invention is to provide a method of forming polyester-melamine laminates which will not peel, blister or otherwise degrade when subject to heat, household chemicals, or abrasion forces normally encountered in lavatories, bathtubs, toilets or similar items of sanitary ware.
In practicing the invention we cross link the polyester chains at least partly with allyl melamine monomer instead of the usual styrene. When the melamine resin glaze is subsequently applied to the polyester the NH.sub.2 groups in the allyl melamine cross linking agent serve as reactive sites for bonding with the melamine glaze coating. The formed laminate exhibits improved resistance against peeling, blistering or surface cracking. We believe that the best product results when the cross linking agent is entirely allyl melamine; however, it is presumed that the cross linking agent could include a minor percentage of styrene or other conventional cross linking agent if cost considerations were paramount.